What happened
Following a five-month period of inactivity, an aircraft was undergoing a maintenance test flight to evaluate the performance of newly installed higher-horsepower engines. The flight proceeded normally through the initial stages, with observers noting two successful touch-and-go landings. However, during subsequent maneuvers within the traffic pattern, the aircraft struggled to maintain sufficient airspeed and altitude.
Witnesses on the ground, including an aircraft mechanic, noted that the plane exhibited a leftward yaw. During this period, sounds were heard that suggested irregular propeller pitch changes, specifically consistent with the Beta range. The aircraft subsequently entered a stall and struck trees in a marshy, wooded region located approximately one mile from the airfield. The wreckage settled in a near-vertical position of roughly 80 degrees.
Findings
An inspection of the wreckage showed no evidence of mechanical failures occurring prior to the impact. While the engines and propellers appeared to be operating with symmetrical power and blade angles at the moment of impact, the lack of flight data recorders and the state of the debris prevented a more detailed analysis. Investigators were unable to confirm the specific cause of the observed yawing or the unusual propeller noises reported by witnesses before the stall.